Acoustic guard



Nov. 7, 1944. Q ROSEN A 2,361,963

ACOUSTI C GUARD Filed March 8, 1945 Lgiof INVICN TOR.

' Our/6e @sen /ai'l' Patented Nov. 7, 1944 UNITED STATES PATENT OFFICE (Granted under the act of March 3, 1883, as

' amended April 30, 1928; 370 O. G. 757) 18 Claims.

The invention described herein, if patented, may be manufactured and used by or for the Government for governmental purposes, Without the payment to me of any royalty thereon.

The present invention relates to acoustic devices. More specifically, valve and filter of unique design adapted to protect the human ear from the noises of warfare, particularly blasts of explosives or other sounds of extreme intensity that might otherwise seriously damage the ear and undermine the nervous system.

The principal object of the invention is to provide a two stage mechanism so that ordinary conversations, commands, and all sounds below a level of 85 decibels are fully audible, yet so the device becomes progressively more and more impervious to sound as the intensity of sound increases above 85 decibels.

Another important object of the invention resides in the provision of an acoustic guard functioning to filter out a large percentage of audio frequencies above 1000 dv. and thereby eliminate the nerve racking fraction of the sound spectrum.

A further object of the invention resides in the provision of a guard which progressive y shuts the sound passage to the ear canals as the sound approaches the pain threshold, so that more and more entrance energy is absorbed in the guard, thereby protecting the ears and the communicating auditory nerve from shock, concussion, trauma and detonation.

Another important object of the invention is to provide a small simple acoustic guard of such size that one of the guards may .be worn in each ear by a soldier in combat without impeding his movements.

A further object of the invention is to provide an acoustic guard as above wherein the guard structures comprise small disk shaped cases with detachabl adapter fittings, so that they may be readily inserted into or removed from the ear.

A further object of the invention is the provision of a guard of simple and rugged construction, fully dependable for the extreme uses to which it is put, entirely mechanical, automatic, and requiring no source of energy extraneous to itself.

The foregoing and other important objects are accomplished in the present invention by the provision of a small, hollow, non-vibratory case having an adapter to conform to the shape of the ear, so that it may be fitted into the ear of the wearer; the case including sound filtering and deadening means including a series of sound it discloses an acoustic valves, so that sounds entering the device are selectively transmitted to the ear, that is, the lesser sounds are transmitted without loss, but sounds of greater intensity are blocked Before entering into a detailed description of the mechanical arrangement of the device chosen as illustrative of the principles of this invention, it is believed pertinent to point out the importance of protecting those in the armed service,

civilians in the presence of excessive noises of war, air raid Wardens, firemen, nurses, ambulance drivers and others, from the serious shock and neurosis incident to excessive noises of combat.

Professor Vern O. Knudsen, acoustics expert of the University of California, recently made the statement:

The noises of tanks and high powered airplanes, if long endured, will induce tinnitus and interfere with physiological functions, and artillery and machine-gun fire and repeated blasts of nearby rifles may cause \both temporary and permanent loss of hearing. Explosions of bombs and shells will not only rupture the ear drum and destroy other organs of the ear but result in shell shock.

Similarly, the Evening Public Ledger, Philadelphia, Pennsylvania, editorially states (August 25, 1941) Noise as a weapon Disquieting in more ways than one was a recent demonstration in Washington, intended to show how soldiers may 'be accustomed to the noises of battle before they are actually under fire. The boom of cannon, the whine of shells, the rattle of machine guns and numerous other noises were amplified to the point where the uproar of an actual battle might have been sweet relief. The reason for training fighting men in this fashion is that noise is bad for the nerves. The Nazis, indeed, have used loud speakers to terrify their enemies before an attack. So American soldiers are to be immunized against battle noises by giving them an overdose in advance. If"

they are not driven deaf they may then be able to stand the racket of real war without flinching.

The sweet and distant dream of peace on earth is now made lovelier by the hope that someday .the world will also be quiet again. For this is a very noisy war and it is no secret that the noisier it can 'be'made the more likely it is to shatter morale and drive men mad with nervous disorders. vWe shall be very weary of noise when the war is done and perhaps determined to put an end to it, so far as possible, in the peaceful occupations and private lives of a world at peace. Thus it appears that there is a crying need for protection of this kind in view of the increasingly greater degree of noise attending present day warfare. It is a recognized fact that such protection will enhance the morale and increase the efficiency of armed troops. Further, since the ear is only second to the eye in stimulus sensitivity, it is important to protect the aural acuity of person in the presence of excessive noises to prevent panic and to insure these persons against tone deafness and other serious disabilities. It is also submitted that adequate protection will reduce hospitalization due to neurosis and shock and, by eliminating fear in the soldier will keep him aware and alert to the tell-tale noises of combat and commands and other sounds which will not injure him. Panic among civilians subjected to the din of war also can be reduced, and the efficiency of airplane mechanics and workers in noisy industrial plants may be increased.

Despite the recognized need for this type of protection, no prior device known to this applicant has met with any degree of success. It is believed that this situation results from attempts to use various types of plugs that act to muffle all sounds uniformly. Obviously, if these accomplish the desired reduction of intense sounds, they render ordinary sounds completely inaudible. This defeats the purpose of the device, since, in the case of a soldier, it renders him completely incapable of understanding commands.

In the preferred embodiment of the invention illustrated in the drawing of this application, and chosen as illustrative of the inventive principles, the desired results are accomplished by providing a casing having a sound passage inincluding exterior and interior sound ports, together with a series of sound valves and means to actuate the valves. It is contemplated that for the most satisfactory operation, the means for actuating the sound valves should be responsive to the very sounds that are to be muffled. To this end, a vibratory diaphragm is associated with the sound valves, and is arranged to alternately close each of these valves when vibrating. The diaphragm is sufficiently stiff so that it will not vibrate preceptibly except under the influence of sound of great magnitude. It is also provided with by-pass perforations, so that when the diaphragm is not vibrating, ordinary sounds of low intensity may pass unrestrictedly from the exterior sound port to the ear.

Referring now more particularly to the drawing:

Fig. 1 is a side elevational view of a preferred embodiment of the invention in position, and

Fig. 2 is an enlarged central sectional view thereof.

As illustrated, the device includes a hollow casing which may be of any non-vibratory material, molded plastics having been found entirely satisfactory. This case may be molded in a single piece if desired, or it may be formed in two opposite halves l and H. In either event, the casing serves to define an internal chamber 12 and act as a support for the peripheral edge I 3 of a vibratory diaphragm Id. The diaphragm 14 includes a pair of closure surfaces (5 and H5 positioned at the center of the diaphragm and on its opposite side faces. If desired, these may be separate pieces of material secured to the 0pposite sides of the diaphragm, as illustrated. The

diaphragm I4 is also provided with a pair 01 bypass apertures l1 and I8, the purposes of which will be more fully described in later paragraphs. It is believed that successful results may be obtained by any one of several types of diaphragms, but a single sheet of cellulose acetate of a thicknes of .018 inch has been found to give excellent performance.

' An outer sound port fitting 2| is fitted into the casing l0 and extends inwardly into the chamber l2 to a point slightly spaced apart from the closure surface l5 of the diaphragm. The opposite end of the fitting extends outwardly beyond the surface of the housing, and is reinforced by a ring 22. The fitting 2| includes a small sound port 23 terminating at its outer end in a conical or bell shaped portion 24 on the outside of the case. Since the inner end of the fitting 2! is in closely spaced relationship with the closure surface l5 of the diaphragm these parts cooperate to act as a valve, to close the sound port 23 when the diaphragm vibrates sufficiently in bring the closure surface l5 into contact with the end of the fitting 2|.

The casing is provided with a similar fitting and sound port on the interior side. The interior fitting 25 is secured in the center of the casing H and extend into the chamber 12 to a point closely spaced apart from the closure surface 16. An interior sound port 26 extends through the fitting so that the inner end of the fitting 25 and the closure surface I6 cooperate to act as an inner sound valve.

The spacing between the ends at the fittings 2| and 25 i subject to some variation, but a space of about .01 inch on each side of the closure surfaces of the diaphragm gives complete satisfaction.

The outer end of the fitting includes screw threads 21 so that an adapter base 28 may be threaded on to the outer end of the fitting,

The adapter base serves a double purpose. First, it serves as a clamping nut to clamp the washers 3| and 32 against the central portion of the resilient ear pad 33 and thus secure the pad in position to lie against the outer ear of the wearer and assist in excluding sound. Secend. it acts as a mounting for the ear adapter 34. To this end the adapter base is provided with a groove 35 to receive the snap ring 36 of the adapter. The external shape of the adapter 34 is formed to fit the auditory meatus of the ear, so that the entire device may be inserted in the human ear and will be maintained in position by the engagement of the adapter with the irregular surfaces of the car, as well as by auxiliary supporting means such as the harness 3'1 illustrated in Fig. 1. It is, of course, contemplated that various sizes and shapes of adapters may be provided to fit different ears, and that each adapter will include an opening 38 to establish auditory communication between the sound port 26 and the ear canal.

The operation of the device is as follows:

When the normal sounds having an intensity of less than decibels strike the outer surface of the device, they will pass unrestrictedly through the exterior sound port 23 and, since the closure surface i5 is spaced slightly away from the end of the sound port, the sound waves may pass through the internal chamber l2 of the casing, through the by-pass ports I! and 18 in the diaphragm and thence through the interior sound port 26 and passage 38 to the ear canal. Thus in the normal sound range the device permits the mands, or any tell-tale sound of battle. I

low intensity sound are not only fully audible, but they are more clearly audible than they would be accuses 3 passage or sound waves from the atmosphere into the ear canal and enables a person wearing the device to hear ordinary conversation, spoken com- I These tq the naked car because the device causes a masking of all external background noises and sounds. thereby making the direct sound entering the ear through the device more articulate. It m has been found that in places where the percent articulation was '10, this device raises the percent articulation to 85 and 90%.

Whena sound of great intensity occurs, however, the sound waves entering the outer sound port 23 will strike the diaphragm M with sufficiently great energy to cause vibratory movement of the diaphragm. The vibration of the diaphragm will alternately move the closure surface l5 toward the fitting 2| to restrict the outer sound port 23 or move the closure surface It toward the fitting 25 to restrict the inner sound port 26. When either of these sound ports is restricted it is obvious that the path of the sound waves will be partially blocked and that the sound 25 will be audible only to a very limited degree. As

the intensity of the sound waves impinging the device is increased the movement of the diaphragm will be correspondingly greater, so that sounds of intensity approaching the pain threshold will cause the diaphragm to completely close the sound ports. Thus any sounds of an intensity which could injure the ear and the attendant train of nerves actuates the sensitive diaphragm and vibrates ittoand fro. The diaphragm vibrates successively from one port to the other, alternately closing off one and then the other. This alternate closing of the two spaced ports has been found to effectively block the transmission of a sound wave through the sound. passage tophysical damage to the inner ear.

The exact form of the device illustrated in the g themardinthesamepositiomthencisewasot the nature of a thud at a far distance. Wearing the guard and with one ear directly in contact with the barrel of the gun, the discharge of the gun resembled a dull thud with no distress attendingthewearer.

From the foregoing it should be apparent that the present disclosure accomplishes the aforementioned obiects of the invention in an exceptionally satisfactory manner. It is of extreme simplicity, and not likely to get out of order. It requires no calibration after it leaves the source of manufacture. It is foolproof, requiring no knowledge of its operation to permit its successful use. It can be manufactured and assembled by mass production methods and at moderate cost.

The preferred embodiment of the device illustrated has been designed particularly to protect the ears of military personnel under conditions,

7 spectfully requested that the scope of the inventive teachings of this disclosure be regarded as limited only by the language of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In an acoustic guard, means adapted to substantially close the human ear, a sound passage through said means communicating with the ear and the atmosphere, a sound-responsive vibrating element in said passage adapted to be enersized by sound waves in the atmosphere, and means responsive to the vibratory movement of said vibrating element to restrict said sound passage.

2. In an acoustic guard, means adapted to substantially close the human car, a sound passage through said means communicating with the ear and the atmosphere, 2. sound-responsive vibrating by sound waves in the atmosphere, and means drawings oi the application has been chosen as 50 responsive to the vibratory movement of said vi- One test was made by means of a 60-cycle g audio-frequency oscillator with a capacity range of from db. to 120 db. The device was found to be fully audible up -to 85 db. and providing a noise reduction of db. at 115 db. It was also found to completely filter out the nerve-rackin w fraction of the sound spectrum above 1600 dv.

In another test an acoustometer was employed and a comparison was made between the nak ear and the ear with the guard. It was found that for all frequencies from 500 dv. to 3.500 d the noise level had to be raised an avera of 5 decibels when the guard was used. as comparedv with the naked ear, and that this difference progressively increased as t e sound frmuencv increased, with a marked difference at 2.500 dv.

In still another successful test, a standard shotgun was fired in the open air. Standing 0pposite the barrel of the shotgun and five feet therefrom, the noise of the shotgun in the naked ear was suificient to make one jump. Wearing 76 stantially close the human car, a sound passage brating element to restrict said sound passage alternately at two points spaced apart from each other. I

' 3. In an acoustic guard, means adapted to substantially close the human ear, 2. sound passage through said means communicating with the ear and the atmosphere, a sound-responsive vibrating element in said passage adapted to be energized by sound waves in the atmosphere, and means responsive to the vibratory movement of said vibrating element to restrict said sound passage at a plurality of points spaced apart from each other.

4. In an acoustic guard, means adapted to substantially close the human car, a sound passage through said means communicating with the ear and the atmosphere, a sound-responsive vibrating element in said passage adapted to be energized by sound waves in the atmosphere, and means responsive tothe vibratory movement of said vibrating element to periodically restrict said sound passage in synchronism with the movement of said sound-responsive element.

5. In an acoustic guard, means adapted to subthrough said means communicating with the ear and the atmosphere, a sound-responsive vibrating element in said passage adapted to be energized by sound waves in the atmosphere, and means responsive to the vibratory movement of said vibrating element to progressively restrict said sound passage and increase the restriction of the actuating said muilling means.

7. In an acoustic guard, means adapted to substantially close the human ear, a sound passage through the means and communicating with the ear and the atmosphere, normally inoperative muflling means at a plurality of points in said passage, said muflling means being spaced apart from each other, and means for actuating said muilling means.

8. In an acoustic guard, means adapted to substantially close the human ear, a sound passage through the means and communicating with the ear and the atmosphere, normally inoperative muiiling valve means at a plurality of points in said passage, said muifiing valve means being spaced apart from each other; and means for alternatively actuating said muflling valve means in synchronism. 9. In an acoustic guard, a casing provided with a sound passage, said passage having sound mufiiing means associated therewith, a harness adapted to secure said casing exteriorly of the human ear and sound restricting means adapted to substantially close the ear against sound, other than that entering through the passage; said sound restricting means including an inner closure device associated with the meatus of the ear and having a sound passage forming a continuation of said first sound passage, together with marginal sound restricting means extending marginally around the casing between the casing and the outer car, so that when the casing is held against the ear by the aforementioned harness the marginal sound restricting means will contact the outer ear of the wearer, whereby the inner closure device and the outer means will cooperate to provide dual means to close the ear canal against all sounds other than those admitted through the sound passages of the guard,

10. In an acoustic guard, a casing provided with a sound passage, said passage having sound muftling means associated therewith, a harness adapted to secure said casing exteriorly of the human ear and sound restricting means adapted to substantially close the ear against sound other than that entering through the passage; said sound restricting means including an inner adapter shaped to conform to the convolutions of the meatus of the ear and adapted to be fitted within the ear meatus, said adapter including a sound passage in communication with the sound passage of said casing so that, when the casing is held against the ear by the aforementioned harness the inner adapter will be secured in position in the ear of the wearer, whereby the sounds admitted through the sound passage of the guard will be transmitted to the ear through the sound passage of the adapter.

11. In an acoustic guard, a casing provided with a sound passage, said passage having sound muining means associated therewith, a harness adapted to secure said casing exteriorly of the human ear and sound restricting means to substantially close the ear against sound other than that entering through the passage; said sound restricting means including an inner adapter shaped to conform to the convolutions of the meatus of the ear and adapted to be fitted within the ear meatus and marginal sound restricting means comprising a relatively soft resilient pad secured to the aforementioned casing and extending marginally around the casing between the casing and the outer ear, so that when the casing is held against the ear by the aforementioned harness the marginal pad will lie in tight, slightly compressed relationship with the outer ear of the wearer, whereby the mner adapter and the outer pad will cooperate to provide dual means to close the ear canal against all sounds other than those admitted through the sound passage of the guard.

12. In an acoustic guard, an adapter fitting shaped to conform to the internal convolutions of the human ear and provided with a sound port extending through the adapter fitting and communicating with the auditory canal of the ear; a casing attached to the adapter fitting and including an interior sound port in communication with the sound port of the aforementioned adapter and an exterior sound port in communication with the atmosphere around the casing, a soundresponsive vibrating element in said casing adapted"*-to be energized by sound waves entering the casing from the atmosphere through said exterior sound port, and muiiling means responsive to the I vibratory movement of said vibrating element to restrict the opening of at least one of the aforementioned sound ports.

13. In an acoustic guard, an adapter fitting shaped to conform to the internal convolutions of the human ear and provided with a sound port extending through the adapter fitting and communicating with the auditory canal of the ear; a casing attached to the adapter fitting and including an interior sound port in communication with the sound port of the aforementioned adapter and an exterior sound port in communication with the atmosphere around the casing, a sound-responsive vibrating element in said casing, said vibratory element comprising a flat circular diaphragm adapted to be energized by sound waves entering the casing from the atmosphere through said exterior sound port and muiiiing means responsive to the vibratory movement of said vibrating element to restrict the opening of at least one of the aforementioned sound ports.

14. In an acoustic guard, an adapter fitting shaped to conform to the internal convolutions of the human ear and provided with a sound port extending through the adapter fitting and communicating with the auditory canal of the ear; a casing attached to the adapter fitting and including an interior sound port in communication with the sound port of the aforementioned adapter and an exterior sound port in communication with the atmosphere around the casing; a sound-responsive vibrating element in said casing, said vibratory element comprising a flat circular diaphragm adapted to be energized by sound waves entering the casing from the atmosphere through said exterior sound port and muiiiing means responsiveto the vibratory movement of said vibrating element to restrict the opening of at least one of the aforementioned sound ports, the center portion of said diaphragm said adapter, and a sound port extending being adjacent to but slightly spaced apart from said sound ports. 7

15. In an acoustic guard, an adapter fitting shaped to conform to the internal convolutions of the human ear and provided with a sound port extending through the adapter fitting and communicating with the auditory canal of the ear; a casing attached to the adapter fitting and including an interior sound port in communication with the sound port of the aforementioned adapter and an exterior sound port in communication with the atmosphere around the casing, a sound-responsive vibrating element in said casing, said vibratory element comprising a fiat circular diaphragm adapted to be energized by sound waves entering the casing from the atmosphere through said exterior sound port, the center portion of said diaphragm being adjacent to but slightly.

spaced apart from said sound ports, and a bypass orificeinterconneoting the opposite sides of said diaphragm, and muifiing means responsive to the vibratory movement or said vibrating element to restrict the opening 0! 'at least one of the aforementioned sound ports.

16. In an acoustic guard, an adapter fitting shaped to conform to the internal convolutions of the meatus of the human ear, a socket in said adapter, and a sound port extending through the adapter fitting between the said socket and the auditory canal of the ear; .a casing provided with a projecting stud, said stud adaptedto fit in detachable relationship with the aforementioned socket in the adapter whereby the casing may be attached to the adapter fitting, a hollow chamber in said casing, an interior sound port connectingthe hollow chamber of said casing with the aforementioned adapter, and an exterior sound port connecting the hollow chamber of said casing with the atmosphere, a soundresponsive vibrating element consisting of a thin fiat flexible diaphragm in said hollow chamber and having its marginal edges mounted in casing on its center to divide the hollow chainber into an inner portion and an outer portion, said diaphragm being adapted to be energized by sound waves entering the casing from the atmosphere through said exterior sound port,

and muffiing means responsive to the vibratory movement of said vibrating element, said means comprising sound valves terminating said sound ports, and means located on the opposite side or said diaphragm and actuated by said diaphragm, to restrict the openings of the aforementioned sound ports alternately in rapid succession upon. the vibration of said vibrated element. 7

1'1. In an acoustic guard, an adapter fitting shaped to conform to the internal convolutions or the meatus of the human car, a socket in said.

diaphragm in through the adapter fitting between the said socket and the auditory canal of the ear; a casing having coupling means consisting of a stud adapted to fit in detachable relationship with the aforementioned socket in the adapter whereby the casing may be removably attached to the adapter fitting; and a marginal pad of resilient material secured between the casing and the adapter fitting and positioned'to lie against the outer ear and seal the ear against sound; and a harness adapted to secure the casing and marginal pad against the car; a hollow chamber in the casing, said hollow chamber including an inner portion and an outer portion, with an orifice therebetween an interior sound port in said chamber connecting the inner portion of the hollow chamber with the sound port of the aforementioned adapter, and an exterior sound port connecting the outer portion of the hollow shaped to conform to the internal convolutions of the meatus of the human ear, a socket in said adapter, and a sound port extending through the adapter fitting between the said socket and the auditory canal of the ear; a casing having coupling adapted to fit in detachable relationship with the aforementioned socket in the adapter whereby the casing may be removably attached to the adapter fitting; and a marginal pad of resilient material secured between the casing and the adapter fitting and positioned to lie against the outer ear and seal the ear against sound: a hollow chamber in the casing, a sound-responsive vibrating element consisting of a thin fiat said hollow chamber, the diaphragm having its marginal edges mounted in said casing to divide the hollow chamber into an inner portion and an outer portion; a bypassorifice in said diaphragm interconnecting the inner and the outer portions of said hollow chamber; and a pair of valve seats located on the opposite sides of said diaphragm and spaced slightly apart therefrom; an interior sound port connecting one of said valve seats with the sound port of the aforementioned terior sound port connecting the other valve seat with the atmosphere, whereby said valve seats function in connection with said diaphragm to restrict the openings of the aforementioned sound ports alternately in rapid succession in response to vibratory movements of said diaphragm. MAURICE C. ROBENBLA'I'I'.

means consisting of a stud, said stud.

adapter, and an ex- 

